REDMOND, Wash. — When Microsoft was developing Cortana, a virtual assistant for its mobile operating system that was unveiled Wednesday, the company thought, naturally, about how it could improve on Siri, Apple’s sometimes bumbling assistant for the iPhone.

Its development teams studied other assistants too — actual human assistants, those keepers of executive calendars and intercepters of phone calls. After interviews with several of them, Microsoft resolved that virtual assistants need to do a better job of anticipating their bosses’ needs.

“Siri is this anthropomorphized character, but Siri doesn’t know you personally,” Joe Belfiore, corporate vice president of Microsoft’s operating system group, said in an interview.

Mr. Belfiore showed the results of its work on Wednesday at an event for software developers in San Francisco held by Microsoft. Cortana is the most high-profile feature of Windows Phone 8.1, a soon-to-be-released update to Microsoft’s mobile phone operating system.

It’s another way in which Microsoft is seeking to narrow the technological gap between its competitors and Windows Phone, which is a distant third among smartphone operating systems, accounting for 3 percent of worldwide shipments in the fourth quarter, according to IDC, the technology research firm.

Late last week in a conference room at the company’s headquarters, Mr. Belfiore demonstrated how Cortana offers all the Siri-like basics, with a number of its same shortcomings. Mobile phone users can use her to set calendar appoints with natural voice commands (“Schedule a phone call with Jim at 2 P.M. tomorrow.”)

Ask Cortana basic trivia — “How old is Barack Obama?” — and she responds with the correct answer in a congenial, synthesized female voice. But ask her when Barack Obama was elected president — a question with two correct answers — and she gets stumped, displaying a list of web search results on the topic so you can do the leg work yourself.

Mr. Belfiore showed how Cortana tries to go beyond Siri to figure out what mobile phone users want before they ask for it. If you keep searching for N.C.A.A. basketball scores, local traffic conditions and news on the Washington State mudslide, she will start to proactively display fresh data about those topics prominently.

With permission, Cortana can examine a user’s email to look for airline reservations, warning them if a flight is delayed. If traffic to the airport is horrendous on the day of departure, Cortana will notify users that they should get in their cars early. When you land in Mexico, Cortana, without prompting, will display the local currency exchange rate, provide an airport map and offer a link to an English-Spanish translation app.

Cortana is named after a virtual character in Halo, Microsoft’s science-fiction video game series, that uses her encyclopedic knowledge about the universe to help the game’s protagonist, Master Chief. The actress, Jen Taylor, who does the voice for the character, also provided recordings for the phone assistant’s voice.

Only when Microsoft’s new software is in use by the masses will it become clear whether it has a real edge on Siri. Apple’s virtual assistant was ridiculed, especially during its early days, for performance problems that rendered it unavailable when people wanted to use it. Those early impressions have been hard for Siri to shake, even as Apple has improved its technology.

Microsoft appears to be making Cortana more open to independent app developers than Apple has with Siri. People will be able to use voice commands to watch a television show on Hulu and to compose and send tweets.

Microsoft has also given Cortana a sense of humor. Last week, Marcus Ash, a program manager for Windows Phone, asked her to sing a song and she belted out a verse from “Danny Boy.”